Moving bed heat exchangers use valves to control the flow of solids through them. Various types of mechanical valves such as ball valves, gate valves, sluice valves and rotary valves can be used for flow control of the solids. However, these valves have moving parts that contact each other and ash and particles passing through the moving bed heat exchanger, and these parts often undergo wear over time that reduces their ability to control the flow of solids. In addition, closing these valves with the solids in their midst poses problems that pertain to exercising active control when desired.
In addition, special design considerations need to be given to the fact that the components of the valve need to function and survive at extremely high temperatures. The solids (e.g., ash) leaving the moving bed heat exchanger is frequently at temperatures of greater than 1500° F.
It is therefore desirable to develop a flow control system for the moving bed heat exchanger that can control the flow of solids at temperatures of 1500° F. or greater without any wear.